In recent years, progress has been made in the development of occupant protection apparatuses for protecting occupants when collision energy acts on a vehicle. As a part of this type of occupant protection, efforts are being made to develop an occupant knee protection apparatus for a vehicle whereby knees are protected by mitigating collision energy that acts on the knees of an occupant.
For example, efforts are being made to develop occupant knee protection apparatuses for a vehicle provided with a passive energy-absorbing structure that has a knee protection member in the front area of the vehicle interior. When collision energy acts on the vehicle from the front direction, the knees of the occupant move forward due to inertia and make contact with the knee protection member. The contact force can be absorbed and the knees protected when the knee protection member is elastically deformed by the impact force (contact force).
There are also many techniques for more actively protecting knees such as that disclosed in Japanese Patent Laid-Open Publication No. 2001-122061. A general overview of the conventional occupant knee protection apparatus for a vehicle described in Japanese Patent Laid-Open Publication No. 2001-122061 is described with reference to FIG. 10 hereof, schematically illustrating the conventional occupant knee protection apparatus.
The conventional occupant knee protection apparatus for a vehicle 100 shown in FIG. 10 has a knee protection member 103 that is movable in the front/rear direction of the vehicle body and is mounted on the instrument panel 102 of a vehicle 101.
In accordance with the occupant knee protection apparatus for a vehicle 100, when the ignition switch is switched on, the distance from the knee protection member 103 to the knees 106 of the occupant 105 seated in a seat 104 is detected by using a position detector 107, and the knee protection member 103 is moved toward the knees 106 by using an electric motor so that the distance is brought to a prescribed fixed value.
In other words, the movement distance of the knees 106 during a collision can be reduced by reducing the gap between the knee protection member 103 and the knees 106.
When collision energy acts on the vehicle 101 from the forward direction, the knees 106 of the occupant 105 move forward a distance equal to the above-described fixed value, and strike the knee protection member 103. The knee protection member 103 absorbs the collision energy that acts on the knees 106 by being displaced in the forward direction of the vehicle body in accordance with the impact force (collision energy) of the knees 106. As a result, the knees 106 can be protected.
In the conventional occupant knee protection apparatus for a vehicle 100 described above, however, there is no change in the fact that the structure is a passive energy-absorbing structure in which the knee protection member 103 is displaced in the forward direction of the vehicle in accordance with the impact force of the knees 106 on the knee protection member 103.
In an actual collision, the deceleration of the vehicle 101 after collision energy has acted on the vehicle is not necessarily fixed and often varies in a complicated manner. Even if the gap between the knee protection member 103 and the knees 106 is set in advance to be a fixed value, the effect of the inertia of the knees 106 varies in the course of events after a collision. However, such a passive energy-absorbing structure still has room for improvement so that the desired energy-absorbing characteristics can always be stably assured even if the initial collision velocity and deceleration of the vehicle 101 at the point of collision has varied.
If the force at which the knee protection member 103 starts to be displaced in the forward direction of the car, i.e., the displacement start force, is set to a low level, the load on the knees 106 and thighs can be reduced. When the displacement start force is low, however, the distance the occupant 105 moves forward while seated increases, i.e., the forward movement distance increases.
There is, therefore, also a need for a technique whereby the forward movement distance of the occupant can be reduced.